/*
 * MapFilter.java May 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.filter;

import java.util.Map;

/**
 * The <code>MapFilter</code> object is a filter that can make use
 * of user specified mappings for replacement. This filter can be
 * given a <code>Map</code> of name value pairs which will be used
 * to resolve a value using the specified mappings. If there is
 * no match found the filter will delegate to the provided filter.
 *
 * @author Niall Gallagher
 */
public class MapFilter implements Filter {

    /**
     * This will resolve the replacement if no mapping is found.
     */
    private Filter filter;

    /**
     * This contains a collection of user specified mappings.
     */
    private Map map;

    /**
     * Constructor for the <code>MapFilter</code> object. This will
     * use the specified mappings to resolve replacements. If this
     * map does not contain a requested mapping null is resolved.
     *
     * @param map this contains the user specified mappings
     */
    public MapFilter(Map map) {
        this(map, null);
    }

    /**
     * Constructor for the <code>MapFilter</code> object. This will
     * use the specified mappings to resolve replacements. If this
     * map does not contain a requested mapping the provided filter
     * is used to resolve the replacement text.
     *
     * @param map    this contains the user specified mappings
     * @param filter this is delegated to if the map fails
     */
    public MapFilter(Map map, Filter filter) {
        this.filter = filter;
        this.map = map;
    }

    /**
     * Replaces the text provided with the value resolved from the
     * specified <code>Map</code>. If the map fails this will
     * delegate to the specified <code>Filter</code> if it is not
     * a null object. If no match is found a null is returned.
     *
     * @param text this is the text value to be replaced
     * @return this will return the replacement text resolved
     */
    public String replace(String text) {
        Object value = null;

        if (map != null) {
            value = map.get(text);
        }
        if (value != null) {
            return value.toString();
        }
        if (filter != null) {
            return filter.replace(text);
        }
        return null;
    }
}
